GHS Signal Words: What They Mean and When to Use Them

GHS Signal Word

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GHS signal word is a standard element of the comprehensive Globally Harmonized System of Classification and Labeling of Chemicals (GHS). It is used within the GHS system to communicate the level of severity associated with hazardous materials.

The goal of GHS signal words is to provide a quick warning about the severity of chemical hazards with a single glance. They are mandatory to be present on all GHS-compliant safety labels and safety data sheets. Signal words are always printed in bold font to catch the reader’s attention.

There are two GHS signal words: “Warning” and “Danger”. Each word has a specific meaning and usage depending on the severity of the hazard.

This article will provide a complete guide to GHS signal words, explaining when and how to use each. 

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So, let’s dive in and look at GHS signal words.

What Does the "Warning" Signal Word Mean?

GHS Word Signal of Warning Signal

The “Warning” GHS signal word indicates the presence of hazardous materials with a low to moderate degree of severity.

Chemical products with a “Warning” signal word require special care in handling and usage but are not likely to cause deaths, serious injury, or damage to the surroundings if misused or mishandled.

Even though the severity of a “Warning” signal is considered low to moderate, it is still essential to read and follow the precautionary measures provided with the product. Chemicals with a “Warning” signal word may cause minor or moderate health effects, such as skin irritation, eye and lung irritation, or allergies if not handled carefully.

When is the "Warning" Word Used?

As per the GHS purple book, “Warning” should be used for the following hazards.

  • Fire or projection hazard
  • Flammable gases (belonging to hazard category 2)
  • Flammable aerosol
  • Pressurized containers
  • Flammable chemicals under pressure
  • Gases under pressures
  • Containers with refrigerated gas
  • Flammable liquids and vapours (belonging to hazard category 3)
  • Combustible liquids
  • Flammable solids
  • Some self-reactive substances and mixture
  • Substances and mixtures which in contact with water emit flammable gases
  • Some oxidizing liquids and solids
  • Some organic peroxides
  • Materials corrosive to metals
  • Some acute toxicity substances (inhaled, touched, or ingested)
  • Substances causing skin corrosion or irritation, eye irritation, allergies, and acute organ toxicity
  • Substances and mixtures suspected to cause cancer and reproductive or genetic harm
  • Substances and mixtures causing an acute environmental hazards to the aquatic wildlife
  • Substances and mixtures damaging Ozone

What Does the "Danger" Signal Word Mean?

Danger signal word of GHS Signal Words

The “Danger” GHS signal word is reserved to indicate highly toxic chemicals that have a high degree of severity.

Chemical material with a “Danger” signal word poses an immediate threat to human health and safety, resulting in severe health effects, such as death, serious injury, and damage to the surroundings. These chemicals require extreme caution in handling, usage, storage, and transportation.

When handling chemicals with a “Danger” signal, it is crucial to read and follow all the hazard statements and precautionary statements specified on the product label and Safety data sheet (SDS).

When is the "Danger" Word Used?

As per the GHS purple book, “Danger” should be used for the following hazards.

  • Explosives
  • Extremely flammable gases
  • Chemically unstable gases
  • Extremely flammable aerosol
  • Extremely flammable gases under pressure
  • Oxidizing gases, liquids, and solids
  • Extremely flammable liquid and vapour
  • Flammable solids
  • Self-reactive substances and mixtures that may cause a fire or explosion
  • Pyrophoric liquids and solids
  • Self-heating substances and mixtures
  • Substances and mixtures which in contact with water emit flammable gases that ignite spontaneously
  • Organic peroxides that may cause an explosion
  • Desensitised explosives
  • Extremely toxic substances and mixtures that are fatal if swallowed, contacted, or inhaled
  • Substances and mixtures that cause severe skin burn and eye damage
  • Substances and mixtures causing breathing difficulties or illnesses like asthma
  • Substances and mixtures causing genetic defects and reproductive toxicity
  • Substances and mixtures causing cancers (known carcinogens)
  • Substances and mixtures causing specific target organ toxicity

Where is a Signal Word Located?

A signal word is located at the top of the GHS-compliant label, right after the product or chemical name but above the hazard statement and precautionary statement.

A signal word is printed in bold with all capital letters using large font sizes to make it easily visible and readable even from a distance. They are placed a bit away from other elements or lettering to draw maximum user attention.

Check our dedicated guide on hazard statements to learn about their meaning, importance, and how to use them.

Can a GHS Label Have Multiple Signal Words?

No, a single GHS-compliant label can not have both “Warning” and “Danger” signal words. At a time, only one signal word is used on the label.

The hazard category and hazard classes should always be determined first to decide what signal word should be used on the label. This is normally accomplished by reviewing test results to see how the chemical interacts in various situations and how living beings react to its exposure.

In case multiple hazards are associated with a single product or chemical, the most potential hazard is chosen, and then the appropriate signal word is used on the label.

So, to summarize, if a product has one hazard with the “Warning” signal word and another with a “Danger” signal word, then only the “Danger” signal word should be used on the label.


GHS signal words are an important part of the hazard communication standard. They play an essential role in helping workers recognize hazardous chemicals and take precautionary measures before handling, storing, or using it.

To sum up, GHS signal words are easy-to-recognise words used to indicate the severity of a chemical hazard. There are only two signal words, “Warning” and “Danger”. Within a certain hazard class, “Danger” is used to communicate more severe hazards, while “Warning” is used to communicate less severe hazards.

Signal words are one of six label elements that should be present on the GHS-compliant label. Please refer to our guide on GHS label requirements to learn more about other elements of the GHS label. 

We hope this article has helped you understand GHS signal words and how to use them correctly.

Thanks for reading!

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